Fighting has ravaged Myanmar since the coup, including renewed clashes with ethnic rebel groups as well as the formation of dozens of "People's Defence Forces" now battling the junta.

In its crackdown against dissent, the "military has killed a minimum of 3,500 civilians" and the number of political prisoners has swelled to 20,000, said the report.

It added that at least $1 billion "worth of weapons, dual-use technology, and materials used to manufacture weapons" were brought in by the junta from the day of the coup on February 1, 2021, to December 2022, primarily from suppliers in Russia, China, Singapore, and India.

"These weapons, and the materials to manufacture more of them, have continued to flow uninterrupted to the Myanmar military despite overwhelming evidence of its responsibility for atrocity crimes," said Tom Andrews, the UN Special Rapporteur on Human Rights in Myanmar.

According to the report, the junta imported $406 million in arms and equipment from Russia and $267 million from China, including from state owned entities. Indian companies and state-owned entities accounted for $51 million in goods.

Companies based in Singapore provided an additional $254 million in supplies, while $28 million in equipment came from entities based in Thailand.

"Russia and China-based entities are critical to the Myanmar military for transfers of advanced weapon systems and their spare parts," Andrews wrote.

The imports have easily circumvented international sanctions prohibiting arms trade with Myanmar, according to Andrews.

His report singled out an attack on an opposition-controlled village that killed around 170 people, including children, describing it as an example of a "probable" war crime.

Andrews wrote that a fighter jet dropped two bombs on Pazi Gyi village in central Sagaing region, targeting the opening ceremony of an office of the National Unity Government -- a shadow administration dominated by lawmakers from ousted leader Aung San Suu Kyi's party.

Soon after, two attack helicopters arrived at the village and began firing on survivors and first responders, he added.

"This brutal attack is also another example of how the Myanmar junta is using internationally supplied arms and associated materials to commit atrocities," the report said.

Special rapporteurs are mandated by the UN Human Rights Council but are unpaid, independent experts who do not speak for the United Nations.